Effects of ion insertion on the electronic and electrochemical properties of transition metal oxide and nitride nanostructures
Authors
Joshi, Siddharth
ORCID
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Other Contributors
Bequette, B. Wayne
Dinolfo, Peter
Bae, Chulsung
Chakrapani, Vidhya
Dinolfo, Peter
Bae, Chulsung
Chakrapani, Vidhya
Issue Date
2019-12
Keywords
Chemical engineering
Degree
PhD
Terms of Use
Attribution-NonCommercial-NoDerivs 3.0 United States
This electronic version is a licensed copy owned by Rensselaer Polytechnic Institute (RPI), Troy, NY. Copyright of original work retained by author.
This electronic version is a licensed copy owned by Rensselaer Polytechnic Institute (RPI), Troy, NY. Copyright of original work retained by author.
Full Citation
Abstract
Transition metal oxides (TMOs) are a class of materials that exhibit a large number of interesting properties such as high mobility of lattice oxygen atoms, complex surface chemistry, high thermal and chemical stability. Owing to these properties, TMOs have been used as photocatalysts, electrocatalysts, sensors, lithium ion battery anodes, capacitors and smart windows. The use of TMOs as anode materials for lithium ion batteries has been extensively studied owing to their high specific capacities for storing lithium compared to commercially used anodes such as graphite. However, the lithium insertion process in these electrodes involves reversible phase transformations that cause huge volumetric changes and ultimately leads to structural failure of the anode material. As these materials undergo conversion reactions involving the formation of lithium oxide and metal particles, they are called ‘conversion’ electrodes, as opposed to graphite which stores lithium between its planar hexagonal sheets and is hence called an ‘insertion’ electrode. Unlike TMOs, which have been studied extensively for lithium ion battery applications, transition metal nitrides (TMNs) are a relatively unexplored class of materials that possess exceptional material properties such as high electrical conductivity, high melting points, and high electrocatalytic properties. Many TMNs have also been shown to display high specific capacities, but also act as conversion electrodes leading to poor cycle life and stability. Due to their exceptional properties, it is highly desirable to develop TMN insertion electrodes that display both high specific capacities and stable cycle life. Drawing inspiration from a class of two-dimensional (2D) materials known as MXenes, whose layered structure allows for the easy insertion and removal of lithium ions, one of the main aims of the present work is to synthesize 2D nanostructures of TMOs and TMNs, and to study the mechanism of lithium insertion in electrodes made from these materials. Certain TMOs possess the unusual property of undergoing a sudden transition from the insulating to the metallic state upon the application of externa stimuli such as changes in temperature or application of strain. Vanadium dioxide, (VO2) is a well known material that displays this metal-insulator transition (MIT) when heated above 67 ºC. This transition can also be triggered at room temperature by the application of a voltage bias in the presence of an electrolyte. Although many theories have been suggested to explain the MIT phenomenon in VO2, the fundamental nature of the transition has been a subject of debate. In particular, the role of vacancies is poorly understood. In the present work, we study the effects of ion insertion and the role of vacancies in both temperature induced and electrochemically induced MIT. In summary, studying the effects and mechanism of ion insertion in TMOs and TMNs is fundamental in not only harnessing the exceptional properties of these materials, but also to understanding widely misunderstood phenomena such as metal-insulator transitions.
Description
December 2019
School of Engineering
School of Engineering
Department
Dept. of Chemical and Biological Engineering
Publisher
Rensselaer Polytechnic Institute, Troy, NY
Relationships
Rensselaer Theses and Dissertations Online Collection
Access
CC BY-NC-ND. Users may download and share copies with attribution in accordance with a Creative Commons
Attribution-Noncommercial-No Derivative Works 3.0 license. No commercial use or derivatives
are permitted without the explicit approval of the author.